The thread scheduler

The adaptive partitioning thread scheduler is an optional thread scheduler that lets you guarantee minimum percentages of the CPU's throughput to groups of threads, processes, or applications. The percentage of the CPU time allotted to a partition is called a budget.

The thread scheduler was designed on top of the core QNX Neutrino architecture primarily to solve the following problems encountered in embedded systems design:

to guarantee proper function when the system is fully loaded
to prevent unimportant or untrusted applications from monopolizing the system

Note that it's threads, not partitions, that are scheduled.